Spongeous typewriter ribbon



United States Patent 3,392,042 SPONGEOUS TYPEWRITER RIBBON Hugh T. Findlay and William H. Horne, Lexington, Ky.,

assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York No Drawing. Filed Jan. 25, 1965, Ser. No. 428,892 Claims. (Cl. 117-361) ABSTRACT OF THE DISCLOSURE A supported transfer medium such as a typewriter ribbon has a transfer layer of a porou resin matrix containing ink in the pores which is expressable under the pressure of a type die. The strength and cut resistance of the ribbon is increased by coating a polymer backing layer onto the transfer layer which contains a complexing filler such as channel black which tends to cros link the polymer filller layer into a continuum.

This invention concerns typewriter ribbons in which a resinous transfer medium layer holds fluid marking material in voids and also in which the transfer layer is structurally supported on one side by a supporting composition especially suited to the needs of typing.

In United States patent application Ser. No. 171,188; filed Feb. 5, 1962; now abandoned continuation-in-part application Ser. No. 536,557 filed Mar. 9, 1966 both titled, Transfer Medium and Method for Making the Same, invented by Kenneth H. Froman and the same Hugh T. Findlay who is an inventor herein, and assigned to the same assignee as this patent application is assigned; improvements in the spongeous transfer medium art are disclosed. Basic knowledge of the transfer medium therein described is known to date from 1931, as evidenced by British Patent 392,220. It is therein taught to apply a slurry of film forming material and fluid ink incompatible with the film forming material onto conventional paper to thereby produce a spongeous transfer medium carried by paper. The ultimate product taught is a carbon paper, but that basic technology has been expanded somewhat to the present state of the art.

This invention is not concerned with the transfer layer individually. In fact, the preferred transfer layer is suggested in the above mentioned abandoned application Ser. No. 171,188. With respect to the invention herein described, however, application abandoned Ser. No. 171,188 can be thought to describe a fabrication process to produce a prototype modified significantly with this invention.

The features and advantages of a transfer medium layer of the resinous, spongeous type have become well known. We have discovered, however, at the cost of most extensive experimentation that a most delicate structural balance must exist to form a typewriter ribbon which feeds and handles with optimum response, and yet resists the cutting action of a type die as the type die impacts the typewriter ribbon. We have determined the necessary critical features and in doing so have solved a most significant problem and have obtained what appear to be a highly significant development in this technology.

Specifically, while the above referenced abandoned ap plication Ser. No. 171,188, in which Mr. Hugh T. Findlay was an inventor as he is an inventor herein, teaches for the first time the use of fillers in the transfer layer, in that invention the use of fillers was taught as being desirable. In this invention it should be understood that the use of fillers in the transfer layer is necessary unless compensation for the lack of fillers in the transfer layer is made elsewhere in the structure of the product. The filler in the transfer layer adds desirable stiffness to the ribbon ice and also acts to hold the liquid ink within the transfer layer during normal handling and feeding. Furthermore, criticality exists in this invention in the requirement that the transfer layer be supported by a supporting composition bonded to it, and that the supporting composition be of a resin containing substantial amounts of a complexin g agent or filler having specific properties.

It is believed that the use of a filler in the supporting composition would have been considered undesirable by the prior art. The prior art apparently has reasoned that most fillers would weaken the substrate layer against the cutting action of the type die. Indeed, we believe that most reinforcing fillers do weaken the substrate layer against cutting. Tests on such reinforced layers as graphitenylon and wood flour-nylon have indicated that significant weakening against cutting is created. Therefore, regardless of increases obtained in the yield point of such reinforced resins, type die impact upon them in normal operation as a typewriter ribbon would tend to cut and shred the ribbon. Since a basic feature of the ribbon is reusability, reinforcing fillers in the substrate layer appear to be a highly undesirable additive. It must be realized that since the cutting action of the type die renders the product highly vulnerable to injury, the degree of perfection in processing required in fabricating the supporting layer is significantly increased. The prior art therefore apparently has further reasoned that compounding and applying a substrate layer containing a filler would create unacceptable problems in adequately mixing, wetting, and applying the mixture.

After extensive study and experimentation, we now recognize that the above disadvantages should be tolerated, and that proper fillers should be found. The use of a complexing filler in the support layer should be considered critical. Reinforcing of the transfer layer by the use of a reinforcing filler is also highly desirable. The complexing filler properly used provides a consistency and stiffness to the typewriter ribbon which allows the typewriter ribbon feed mechanism to function as desired. Properly selected fillers also apparently reduce surface attractions of the typewriter ribbons for structures through which the ribbon is moved, although the mechanism for reduction of surface attraction is not well understood.

A complexing filler is one which links with bond-like attractions to the resin of the mixture. A complete network is formed, but not a mechanical one with rigid dimensions. The combination is strong, but yields to a. type die rather than being cut by the type die. Carbon black has been discovered to be a desirable complexing filler for use in this invention. The activity of carbon black in a chemical matrix is thought to depend upon unique surface characteristics of the carbon black, but as with most chemical developments the postulation of a mechanism is not particularly helpful, and reliance must primarily be placed upon careful experimentation.

Particularly beneficial results are obtained when the resinous material used is a polyamide. Regardless of the added difiiculties and expenses incurred by using and processing a polyamide such as nylon, the strength of nylon is significant as compared to that of most other available resins. The final ribbon produced can be quite thin, a highly desirable design criterion for all typewriter ribbons since typewriter ribbons are carried on the typewriter in the limited space provided. An extremely thin ribbon reinforced as herein described results in a typewriter ribbon of significant economic importance since a large writing capability is provided in a small storage space in the typewriter.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention.

INK MIXTURE Component: By wt. percent Carbon black with die precipitate (1686-Paul Uhlich Co.) 6 Carbon black with die precipitate (2451L-Paul Uhlich Co.) Nigrosine oleate (DS2183) 63 Methyl violet base 3 Mixed fatty acid esters (Ohopex R9-Ohio Apex The ink dispersion is obtained by use of the 5xl2-inch three-roll dispersion mill manufactured by the I. H. Day Co., Cincinnati, Ohio. In this device, mixtures are poured to the feed roll and they exit from the take-off roll. To compound the ink mixture, the first four items above listed: that is, the two carbon blacks, the nigrosine oleate, and the methyl violet base; are first processed with five passes through the three-roll dispersion mill. On the first mixing, the input roll is at 150 lbs. pressure and the out put roll is at 200 lbs. pressure as defined by the gages on the I. H. Day mill. On passes 2, 3, 4 and 5 the input roll is at 200 lbs. pressure and the output roll is at 250 lbs. pressure. The 18% by weight of mixed fatty acid esters as designated in the above formula is then added to the dispersed mixture. The entire ink mixture is then mixed vigorously for about minutes with a Cowles dissolver.

It is also beneficial to mix the transfer layer filler into the ink mixture. The filler is technically a part of the transfer layer solution since the entire ink and transfer layer are dispersed together and upon evaporation of the solvent, as described below, the tiller remains mixed with the resin of the transfer layer in significant amounts. Some of this filler also may exist loose in the pores of the transfer layer resin. In fabrication, however, the graphite is added to the above milled ink mixture immediately after the ink mixture has been completely dissolved. Two additional passes are then made through the above described 3-inch by 12-inch three-roll dispersion mill, with the input roll at 200 lbs. pressure and the output roll at 250 lbs. pressure. When this is properly performed, the ink mixture with graphite is permanently mixed and will not settle for an indefinite period of time.

At the time of production of the typewriter ribbon of this invention, a transfer layer solution is compounded. The transfer layer solution is later applied on a temporary substrate in the known manner, after which application the solvents are driven off and the final product partially obtained. The transfer layer solution consists of the following parts.

TRANSFER LAYER SOLUTION Component: Proportions, grams Nylon (Zytel 61) 450 Graphite (007-S) 450 Ink mixture (as above specified) 900 Denatured ethyl alcohol (Jaysol) 3,680

natured alcohol while the mixture remains in the bucket.

This combination is vigorously mixed in a Cowles dissolver while the heat is maintained for about tfive minutes. The heat is turned off and the mixture is continued to be agitated by the Cowles dissolver for 30 to 40 minutes while the entire bucket cools to room temperature. The entire quantity of the above described graphite and ink mixture is added after the cooling is accomplished, and this combination is further mixed with the Cowles dissolver for not less than 15 minutes. Dispersion in this manner completes the compounding of the transfer layer mixture.

The third mixture used in compounding this typewriter ribbon is the support layer mixture. The support layer mixture is made up primarily of nylon and a properly selected filler, preferably channel black. The support layer mixture is composed as follows:

SUPPORT LAYER MIXTURE Components: Parts by wt. Nylon (Zytel 61) 1.5 Denatured alcohol (Jaysol) 12.0 Water 3.0 Channel black (Mogul SCabot Co.) 0.5

The manner of compounding the support layer mixture initially is similar to that for compounding the transfer layer mixture. The alcohol and water are first mixed together in a receptacle and heated to approximately degrees F. Then the nylon is added and mixing is carried on with a Cowles dissolver for about five minutes with heat applied and for 30 to 40 minutes as the mixture is allowed to cool to room temperature. The channel black may be added any time after the nylon has been dissolved. Proper wetting and mixing of the carbon black is essential, and this is obtained by use of a homogenizer. The device used is a 15 M8BA SMDSer. N0. 1230586606, a product of the Manton-Gaulin Manufacturing Co., Inc., Everett, Mass. The homogenizer circulates a fluid mixture through a needle valve arrangement,

in which the mixture is forced through an opening and opposed by a needle, the fluid mixture being thus dispersed as it exits in the shape of a disk. The mixture later settles and is collected. Two passes are made through this homogenizer to complete the compounding of the support layer mixture. The gage is kept between 4,500 and 5,000 to achieve a balance between a maximum mixing and breaking up of agglomerates in the mixture and, on the other hand, a reduced possibility of exceeding allowable operating pressures within the machine by allowing too much pressure to build up at the mixing location in the homogenizer.

The process of applying the mixtures and driving off the solvents to produce the typewriter ribbon is much similar to that described in the above referenced application Ser. No. 171,188. First the transfer layer mixture is placed in a roll coater basin in which an applicator roller of a reversed roll coating applicator is situated. A temporary substrate made of polyethylene terephthalate is played out through the roll coater while the applicator roller applies the transfer medium layer to the temporary substrate. The mechanism leads to a drying oven with appropriate exhaust fans.

It is preferred to execute a complete pass in which a layer of transfer medium is applied to the polyethylene terephthalate film and dried completely. The polyethylene terephthalate film is collected in a roll at the terminal location of the drier. The roll of polyethylene terephthalate with the cured transfer medium is placed in the playout position of the solvent coating apparatus. The basin is then filled with the support layer mixture above described. Then the entire operation is repeated with the applicator roller of the coating applicator this time applying the support layer. The polyethylene terephthalate feeds into the evaporating ovens where the fabrication is completed by the expulsion of solvent from the support layer. When this step is complete, a roll of polyethylene terephthalate substrate containing bulk quantities of the completed ribbon exists. The ribbon can be stripped from the substrate and slit and rolled into typewriter ribbons.

Test runs are made to obtain the thicknesses desired. The amount of material applied to the temporary polyethylene terephthalate substrate is fundamentally controlled by the small cleaning roller located on the applicator roller at a point prior to the point at which the applicator roller contacts the substrate. Different tension on this, along with such factors as ambient temperature and minor changes in viscosity of the mixtures, allows the final coatings obtained to be varied. A test run coating is made and the result is weighed or otherwise observed. This establishes that the thickness is that desired. If the thickness is not correct, the cleaning roll is changed in position or minor modification may be made in the mixture by a technique such as allowing some evaporation to occur.

In fabricating this preferred ribbon, test runs are first made and the proper factors are determined so that the dry transfer layer is from 0.0006 inch to 0.002 inch thick and the dry support layer is from 0.0001 to 0.001 inch thick. The two layers are separate, but bonded together in the final product. Each layer is of relatively uniform thickness within the above described limits. The actual thickness is selected in accordance with the intended use of the ribbon; maximum reuse, for example, being achieved by an increase in the thickness of both layers. A thinner ribbon is most useful to achieve superior print quality at the cost of some decrease in ribbon life. The use of water in addition to denatured ethyl alcohol in the solvent phase of the support layer mixture is significant in that the water changes the solvating characteristics of the mixture in the proper direction so that ink is not leached from the transfer medium layer to the support layer. Transfer of ink into the support layer would weaken the support layer and also waste ink and dirty the type die during typing.

The final preferred product contains two layers, the transfer layer and the support layer. The transfer layer has two opposite sides, one of which is bonded to the support layer, while the second side is unobstructed. In use, a type die impacts the support layer to thereby express the ink mixture from the unobstructed side of the transfer layer onto paper or other receptive material. The ink mixture exists normally in the pores of the transfer layer where it is held as globules.

The channel black is the complexing filler. Other fillers, such as wood flour, may act as reinforcing fillers, but they may not be complexing fillers as defined by this invention. The salient feature of the complexing filler is that it links with the resin used with bonds of the inter-molecular type. These bonds may be an weak as Van de Waals forces, but they have distinct characteristics different from mechanical interconnections. Complexing fillers may differ with the different resins used to practice the invention. Proper complexing fillers are found, however, in accordance with the teachings of this invention, following routine experimentation.

The molecular-type bonds of a complexing filler modify the characteristics of the solidified resin and filler phase. In particular, a complexing filler tends to cross-link the entire resin and filler phase into a continum. The ductility of the product is different from that which would be predicted on the basis of a mechanical linking of the elements. The ductility of a nylon-graphite sheet, for example, was found to be about 7 times that of a comparable nylon-channel black sheet at load levels below and up to the point at which the nylon-graphite sheet stretched somewhat more than 100 percent. Examination of this can be made by stretch tests and graphical plots of the results. Secondly, the solubility characteristics of a resin-complexing filler phase are shifted from that of resin. A nyloncarbon black layer, for example, is significantly less soluble in denatured ethyl alcohol than pure nylon. Measurement of this shift in solubility can be accomplished with state of the art techniques to thereby determine the existance of a complexing filler.

While the invention has been particularly shown and described with reference to a preferred embodiment there of, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

We claim:

1. A supported transfer medium comprising:

a transfer layer having two opposite sides comprised of a resin having a plurality of pores at least partially filled with globules of transfer ink, and

a supporting composition bonded to one of said sides of said transfer layer, said supporting composition being comprised of a polyamide and also being comprised of an amount of carbon black sufficient to link with said polyamide to form a matrix of bonds so that said supporting composition is reinforced and yieldable to sharp edges of an impacting type die.

2. The product as in claim 1 wherein said carbon black is channel black.

3. A supported transfer medium comprising:

a transfer layer having two opposite sides comprised of a resin having a plurality of pores at least partially filled with globules of transfer ink and also comprlsed of a reinforcing filler dispersed through the transfer layer, and

a supporting compoistion bonded to one of sald sides of said transfer layer, said supporting composition being comprised of a polyamide and also being comprised of an amount of carbon black sufficient to 1111K with said polyamide to form a matrix of bonds so that said supporting composition is reinforced and yieldable to sharp edges of an impacting type die.

4. The product as in claim 3 wherein the carbon black is channel black.

5. A supported transfer medium com-pr1s1ng:

a transfer layer having two opposite sides comprised of a resin having a plurality of pores at least partially filled with globules of transfer ink, and

a supporting layer bonded to one of said sides of said transfer layer, said supporting layer being comprlsed of a polyamide and also being comprised of an amount of carbon black sufficient to link said polyamide to form a matrix of bonds so that said supporting layer is reinforced and yieldable to sharp edges of and impacting type die.

6. The product as in claim 5 wherein sald carbon black is channel black.

7. A supported transfer medium comprising:

a transfer layer having two opposite sides comprised of a resin having a plurality of pores at least partially filled with globules of transfer ink and also comprised of a reinforcing filler dispersed through the transfer layer, and

a supporting layer bonded to one of said sides of said transfer layer, said supporting layer being comprised of a polyamide and also being comprised of an amount of carbon black sufficient to link said polyamide to form a matrix of bonds so that said supporting layer is reinforced and yieldable to sharp edges of an impacting type die.

8. The product as in claim 7 wherein the carbon black is channel black.

9. A supported transfer medium comprising:

a transfer layer having two opposite side comprised of nylon having a plurality of pores at least partially filled with globules of transfer ink and also comprised of a reinforcing filler dispersed through the transfer layer, and

a supporting layer bonded to one of said sides of said transfer layer, said supporting layer being comprised of nylon and also being comprised of an amount of carbon black sufiicient to link with Said nylon to form a matrix of bonds so that said supporting layer is re- 7 8 inforced and yieldable to sharp edges of an impacting 3,287,153 11/1966 Schwarz et a1 11736.1 type die. 3,324,072 6/1967 Brignac 260-37 10. The product as in claim 9 wherein the carbon black 3,330,791 7/1967 Mater et a1 260 28 is channel black. 3,336,150 8/1967 Takahashi et a1. 117-361 5 3,337,361 8/1967 La Count 117-36.1

References Cited UNITED STATES PATENTS 3,037,879 6/1962 Newman et a1 1l736.1 3,102,824 9/1963 Newman et a1. 11736.1

EARL M. BERGERT, Primary Examiner.

M. L. KATZ, Assistant Examiner. 

